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TS 710 
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Copy 1 PRICE 25 CENTS 


METAL COLORING 
AND FINISHING 


METHODS OF PRODUCING COLORS ON IRON, 
STEEL, COPPER, BRONZE, BRASS AND 
ALUMINUM-BURNISHING METALS 



MACHINERY’S REFERENCE BOOK NO. 1231 

PUBLISHED BY MACHINERY, NEW YORK 







mnofnioi' 











MACHINERY’S REFERENCE BOOKS 

This book is one of a remarkably successful series of 25-cent Reference Books 
listed below. These books were originated by Machinery and comprise a complete 
working library of mechanical literature, each book covering one subject. The price 
of each book is 25 cents (one shilling) delivered anywhere in the world. 


CLASSIFIED LIST OF REFERENCE BOOKS 


GENERAL MACHINE SHOP PRACTICE 

No. 7. Latlie and Planer Tools. 

No. 10. Examples of Machine Shop Practice. 

No. 25. Deep Hole Drilling. 

No. ,32. Screw Thread Cutting. 

No. 48. Files and Filing. 

No. 50. Principles and Practice of Assembling 
Machine Tools, Part I. 

No. 51, Principles and Practice of Assembling 
Machine Tools, Part II. 

No. 57, Metal Spinning. 

No. 59. Machines, Tools and Methods of Auto¬ 
mobile Manufacture. 


No. 91. 
No. 92. 
No. 93. 
No. 94. 
No. 95. 
No. 96. 
No. 97. 
No. 98. 


Operation of Machine Tools.—The Lathe, 
Part I. 

Operation of Machine Tools.—The Lathe, 
Part II. 

Operation of Machine Tools. — Planer, 
Shaper, Blotter. 

Operation of Machine Tools.—Drilling Ma¬ 
chines. 


Operation of Machine Tools.—Boring Ma¬ 
chines. 

Operation of Machine Tools.—Milling Ma¬ 
chines, Part I. 

Operation of Machine Tools.—Milling Ma¬ 
chines, Part II. 

Operation of Machine Tools.—Grinding 
Machines. 

No. 116. Manufacture of Steel Balls. 

No. 120. Arbors and Work Holding Devices. 

TOOLMAKING 

No. 21. Measuring Tools. 

No. 31. Screw Thread Tools and Gages. 

No. 64. Gage Making and Lapping. 

No. 107. Drop Forging Dies and Die Sinking. 

HARDENING AND TEMPERING 


No. 101. Circular Forming and Cut-off Tools for 
Automatic Screw Machines. 

No. 102. External Cutting Tools for Automatic 
Screw Machines. 

No. 103. Internal Cutting Tools for Automatic 
Screw Machines. 

No. 104. Threading Operations on Automatic 
Screw Machines. 

No. 105. Knurling Operations on Automatic Screw 
Machines. 

No. 106. Cross Drilling, Burringtand Slotting Op¬ 
erations on Automatic Screw Machines. 

SHOP CALCULATIONS 

No. 18. Shop Arithmetic for the Machinist. 

No. 52, Advanced Shop Arithmetic for the Ma¬ 
chinist. 

No. 53. The Use of Logarithms—Complete Log¬ 
arithmic Tables. 

No. 64. Solution of Triangles, Part I. 

No. 55. Solution of Triangles, Part II. 

THEORETICAL MECHANICS 

No. 5. First Principles of Theoretical Mechanics. 

No. 19. Use of Formulas in Mechanics. 

GEARING 

No. 1. Worm Gearing. 

No. 15. Spur Gearing. 

No. 20. Spiral Gearing. 

No. 37. Bevel Gearing. 

GENERAL MACHINE DESIGN 

No. 9. Designing and Cutting Cams. 

No. 11. Bearings. 

No. 17. Strength of Cylinders. 

No. 22. Calculation of Elements of Machine De¬ 
sign. 

No. 24. Examples of Calculating Designs. 


No. 

46. 

Hardening and Tempering. 

No. 

40. 

Flywheels. 

No. 

63. 

Heat-treatment of Steel. 

No. 

56. 

Ball Bearings. 




No. 

58. 

Helical and Elliptic Springs. 



JIGS AND FIXTURES 

No. 

89. 

The Theory of Shrinkage and Forced Fits. 

No. 

3. 

Drill Jigs. 




No. 

4. 

Milling Fixtures. 



MACHINE TOOL DESIGN 

No. 

41. 

Jigs and Fixtures, Part I. 

No. 

14. 

Details of Machine Tool Design. 

No. 

42. 

Jigs and Fixtures, Part II. 

, No. 

16. 

Machine Tool Drives. 

No. 

43. 

Jigs and Fixtures, Part III. 

«•< J No. 

111. 

Lathe Bed Design. 




no. 

112. 

Machine Stops, Trips and Locking De¬ 



PUNCH AND DIE WORK 

*. * 


vices. 

No. 

6. 

Punch and Die Work. 



CRANE DESIGN 

No. 

13. 

Blanking Dies. 




No. 

26. 

Modern Punch and Die Construction. 

No. 

23. 

Theory of Crane Design,. 


AUTOMATIC SCREW MACHINE WORK 

No. 99. Operation of Brown & Sharpe Automatic 
Screw Machines. 

No, 100. Designing and Cutting Cams for the Au¬ 
tomatic Screw Machine. 


No. 47. Electric Overhead Cranes. 

No. 49. Girders for Electric Overhead Cranes. 

STEAM AND GAS ENGINES 

No. 65. Formulas and Constants for Gas Engine 
Design. 


SEE INSIDE BACK COVER FOR ADDITIONAL TITLES 


MACHINERY’S REFERENCE SERIES 

EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF 
MACHINE DESIGN AND SHOP PRACTICE REVISED AND 
REPUBLISHED FROM MACHINERY 


NUMBER 123 

METAL COLORING AND 

FINISHING 


CONTENTS 

Principles of Metal Coloring, by W. J. Kaup - - 3 

Coloring Iron and Steel, by E. F. Lake - 9 

Coloring Non-ferrous Metals and Alloys, by E. F. Lake 15 
Lathe Burnishing of Metals, by William A. Painter - 26 
The Ball Burnishing Process, by Chester L. Lucas - 33 



Copyright, 1914, The Industrial Press, Publishers of .Machinery, 
140-148 Lafayette Street, New York City 




« I * 



APR 22 1914 

©CIA372570 

*iaa> t 





CHAPTER I 


PRINCIPLES OF METAL COLORING 

The subject of metal finishing and coloring has received but scant 
attention in mechanical publications; this is rather surprising when 
we note the inclination of the manufacturers of today to combine this 
artistic treatment with utility, and add contrast of color to the severe 
straight-line plainness of our commercial products, to produce more 
beautiful effects. There is nothing new in metal coloring. Ages ago 
it was old in Japan, and to the Orient we must really turn for original 
authority on successful coloring of metals. 

The purpose of this book is to give to those who are interested the 
results of the experience of a number of authorities in coloring 
metals, solely from the manufacturing side, rather than from the 
chemist’s standpoint. So many conditions enter into the work that no 
law can be laid down by which everyone can obtain the same satis¬ 
factory results, for with everyone the coloring of metals must at first 
be more or less of an experimental nature. A cheap monochrome 
color can be produced by the novice who is unacquainted with the 
metallurgical properties of metals and chemical actions of solutions 
used, but the very fact that the slightest change in the alloy, as well 
as in the strength of the coloring solutions, produces a different shade 
of coloring under the same treatment, makes it essential that the 
operator should have considerable knowledge of metallurgy and chem¬ 
istry for any except the simplest work. 

First, let us consider the different methods and conditions under 
which color can be obtained, viz., by heat-treatment alone; by var¬ 
nishes and lacquers; and by corroding agents or chemical compounds. 
We will treat each under its separate heading, but first will refer 
briefly to the Bunsen burner, by the use of which, together with a pot 
of heavy fish or lard oil and a pair of tweezers, one can color small 
pieces by the heat process. 

The Bunsen Burner 

We will take for granted that some readers, at least, are not ac¬ 
quainted with the Bunsen burner, or at least the principle of its 
operation. The illustration herewith will explain its construction. 
The object of this burner is to procure a flame capable of producing 
great heat, but which will not smoke any vessel or article heated in 
it or over it; by carefully noting the construction, it will be readily, 
seen how this is accomplished. The force of gas, escaping through 
the small aperture at A, draws the air through the holes in the sleeve 
surrounding the jet. The air and gas mix together, consuming 
the carbon produced by the decomposing gases before it becomes in- 

' ■ l \ !> -* <V 

candescent, and producing the flame desired. The air is controlled by 


4 


No. 123—METAL COLORING AND FINISHING 


a sleeve, which turns around the inner tube, thereby increasing or de¬ 
creasing the size of the opening through which the air is drawn. A 
few minutes’ use of the burner will enable anyone to get the flame 
right, but a few points with respect to this may be useful. The flame 
should be about 2 y 2 inches high only; it should not blow; it should 
burn with blue light, showing a defined inner cone of blue-green light 
immediately above which, at point C, the greatest heat is obtained. 



Producing- Color by Heat-treatment 

The work treated over a Bunsen burner is necessarily small, such as 
small screws, bolt heads, washers, pins, etc. The work should be 
thoroughly cleansed from all grease, either by dipping in a strong hot 
lye solution or in alcohol, and then dried in clean sawdust; it is abso¬ 
lutely essential that the entire surface presents the same physical 
condition, to obtain uniformity of color. The work should be subjected 
to the flame immediately above the inner cone of light. Carefully 
watch the varying change of color and withdraw from the heat before 
it quite reaches the blue desired; then hold the work in the air until 
the desired shade appears, and “check” the color change by dipping 























GENERAL PRINCIPLES 


o 


the piece in the oil and allowing it to cool in it. Very good bluing 
can be done in this way by the beginner on pieces of uniform shape, 
but much more skill will be required on pieces where the shape is 
irregular, having large surfaces in one place and small in another, 
when the heat must be confined to the larger part for a longer period 
of time than is necessary for the small parts. In such cases the 
amount of heat contained in the larger part is usually sufficient to 
produce the desired effect in the smaller details after taking the piece 
from the flame. 

Another very common method, especially for flat work, is to heat 
a flat piece of iron or steel of sufficient size to retain the heat for a 
long time and place the piece to be colored on the hot surface, some¬ 
times in direct contact with the hot metal, and at other times on a 
piece of sheet iron placed on the hot piece. When the desired color 
appears, plunge the work into an oil bath. Yet another way is the 
hot-sand method. A pan of sand is heated to a high degree, the 
parts are buried in it and rolled around, and when the required color 
appears it is “checked” as before. In all these methods the colors that 
appear to the eye come in the following order: Pale straw, dark 
straw, brown, purple, blue and green. The processes are identical 
with those of tempering steel by the color method. The wearing life 
of work done by these methods is naturally very short, as the colors 
rub off very quickly by handling. 

Corroding Agents 

We now come to the corroding agents—chemical compounds—by 
which the most successful results are obtained, by the dipping process, 
or “wet coloring,” as it is called. There are many methods known as 
“dry coloring” which have been repeatedly tried; in this compounds 
are mixed together, forming pastes that are applied with a brush and 
allowed to remain any number of hours and then rubbed off, but most 
of these methods are more or less failures. The wet method presents 
many advantages, both as regards economy of time and uniform 
results. 

To color copper articles, such as ash trays, pin dishes, receivers, etc., 
a solution of ammonium sulphide will give the best results to the be-, 
ginner. The greatest variety of colors, from light brown to black, can 
be obtained by this simple method. Use a dilute solution, cold. A good 
working solution is produced by diluting a saturated solution of am¬ 
monium sulphide with 10 to 40 parts of water. A light brown color 
is produced by dipping the work for a very short time in the solution, 
withdrawing it, and allowing it to dry in the air. A darker shade of 
brown is obtained by a longer immersion, according to the color de¬ 
sired, after which the work is allowed to dry in sawdust. To obtain 
a black coloring, allow the article to remain quite a while in the bath, 
and, after removing, dip it in alcohol, after which the alcohol is 
burnt off, leaving a black coating. These colors can be permanently 
fixed by a transparent lacquer. The objection to ammonium sulphide 


6 


No. 123—METAL COLORING AND FINISHING 


is the great care necessary in handling, as it leaves an indelible stain 
upon the fingers, and also has a very obnoxious odor. The ammonium 
sulphide also decomposes in time, depositing sulphur. It should be 
kept in a dark-colored bottle provided with a glass stopper. It is not 
good for brass, being adapted only for copper. 

Another solution for coloring copper which yields very good results 
is: 


Copper nitrate . 1 part 

Water .... 3 parts 


This forms a deposit of copper salt, and, if heated, the salt is de¬ 
composed into a black copper oxide. The greenish tints are obtained 


by the following solution: 

Ammonium carbonate . 2 ounces 

Ammonium chloride .2/3 ounce 

Water .16 ounces 


This solution gives good results on both copper and brass, different 
colorings being obtained by repeated dippings in the solution, allow¬ 
ing ample time between each for the articles to properly dry. 

Many varieties of color can be obtained by different chemical solu¬ 
tions on both copper and brass, but the desirable colors for commercial 
use are dead black and steely gray. 

The following mixture has also given very good results for brass: 
hydrochloric, or more commonly termed muriatic acid, white arsenic, 
and silver. 

Take any given quantity of arsenic, say y 2 ounce, dissolve it in 
strong muriatic acid, and then snip off a small piece of a silver dime, 
if no other silver is at hand. Heat the article to a dull red and dip 
it in the solution; then allow it to remain until cool. This produces 
the dull black result so often seen on mathematical instruments. The 
steely gray is obtained in the same manner, except that the article is 
not heated to such a high temperature as in the preceding case. By 
the arsenic solution many good results are obtained by cold dipping 
also. 

In every case where chemical solutions are used, it is well to re¬ 
member that the slower the rate of deposition the better the results 
from the wearing standpoint; hence, the longer a dilute solution takes 
to deposit its coating, the better the color will last, and that is, of 
course, a very desirable quality. In Chapter III is given a more com¬ 
plete review of the whole subject of coloring non-ferrous metals. 

Cleaning- Old Brass and Copper 

In conclusion, it will be well to touch upon the method of cleaning 
old brass or copper from impurities. The brass articles are strung on 
a wire, which should be of the same material as the articles, and 
dipped in the following solution: 1 part nitric acid, 6 parts muriatic 
acid (hydrochloric acid), and 2 parts water. 

The articles are first dipped in a strong hot solution of soda in 
water, and then into the bath, where they are swirled around for a 







GENERAL PRINCIPLES 


7 


time, removed and rinsed in cold water and dried in sawdust. If the 
metal looks dark and is not quite bright, the nitric acid in the solu¬ 
tion should be reduced. Where many pounds of small brass fittings 
are to be treated, they are put in an earthenware pot containing 
numerous perforations. 

Zinc is often cleaned by dipping into a solution of 16 parts water and 
1 part oil of sulphuric acid, for a few moments, and then washing it 
thoroughly to remove all trace of the bath. 

Coloring- Iron and Steel 

The coloring of copper and brass, especially copper, is for its artistic 
value alone; but from the purely commercial standpoint the coloring 
of iron and steel is of greater value, because it is used for so many 
machine parts and parts of guns, small arms, etc., which are treated 
to produce a blue or black color for the purpose of preserving the 
metal against corrosion, as well as to give it a handsome appearance. 

The following solution will give very satisfactory results with iron 
or steel if carefully treated: Take equal parts of potassium nitrate - 
and sodium nitrate and fuse by heating mixture until completely 
melted. The melting point of the mixed nitrate salts is about 600 
degrees F. Dip the articles first in boiling lye or strong hot soda 
water to thoroughly cleanse them from grease; then dip them in the 
hot mixed nitrate flux, and from there remove them into boiling 
water to rinse off the nitrate. Different temperatures of the solution 
will produce different shades of coloring, and sometimes it will be 
found advisable to use the flux at a temperature as high as 700 
degrees F. 

In many cases where hardened articles are to be treated it would 
not be possible to bring the steel to the desired color by this process, 
because the temperature of the fused nitrates would be so high as to 
draw the temper of the articles. In such cases the old nitric acid 
rusting process is generally resorted to. The nitric acid is placed in 
an earthenware jar and inclosed in a box that can be made practically 
tight by closing the lid. The article is suspended in the box and the 
lid closed, and the fumes arising from the acid oxidize the surface of 
the article; if the article is moistened before placing it in the box, a 
very much more rapid oxidation is assured, saving considerable time. 

Many experiments have been tried with different mixtures for color¬ 
ing iron and steel, where there is danger of drawing the temper of the 
metal; of these the following has proved very successful: A wooden 
box is used, of a size according to the kind of work to be colored. A 
small steam pipe connects with the box, so that a quantity of steam 
may flow into it continuously and moisten the air in the box. A bath 
made of the following ingredients is then placed in the box: 


Iron chloride (muriate tincture of steel). 1 ounce 

Alcohol (spirits of wine). 1 ounce 

Corrosive sublimate (mercury bichloride). % ounce 

Strong nitric acid.ounce 

Blue stone (copper sulphate). Vs ounce 

Water . 1 quart 








8 


No. 123—METAL COLORING AND FINISHING 


The vapor arising from this bath forms a deposit on the articles, 
which are allowed to remain in the receptacle a number of hours and 
rubbed off with a cloth; the operation is repeated if a darker color is 
desired. Very rich coloring can be obtained by this process, after a 
little experimenting, and the temper is not affected. Many other 
methods are included in the detailed descriptions dealing with the col¬ 
oring of iron and steel given in the next chapter. 

Removing 1 Rust from Steel 

A quick method of removing rust from steel parts, which is not 
generally known, is outlined in the following: Rub the surface of the 
piece of work from which rust is to be removed with muriatic acid. 
A convenient way to do this is to dip a match or other small stick 
into the acid and rub it over the surface of the work. This procedure 
is continued for several minutes, dipping the stick in as often as neces¬ 
sary to obtain a sufficient quantity of acid. After this treatment has 
been completed, the work should be washed with a solution of com¬ 
mon washing soda and water and then dried in sawdust. This will 
leave the work free from rust and scratches, but with a dull gray sur¬ 
face. The surface of the metal can be restored to its original color by 
a little rubbing. In one factory this method has been used for several 
years with successful results. 

Varnishing and Lacquering 

Varnishing and lacquering, as being somewhat apart from the sub¬ 
ject matter, will be treated very briefly. The method cannot be used 
to produce an artistic color effect, but is nearly always used for pro¬ 
tecting the surfaces of instruments and machines from discoloration 
by atmospheric influence. In nearly every instance lacquering is used 
only on metal alloys. It might be well in this connection to note the 
discoloring tendencies of metals in alloys, as given by a noted German 
authority. The discoloring action upon metals takes place to the 
greatest extent upon tin and the least upon gold. In the following 
list of metals the action becomes less from the first to the last: 1. 
Tin; 2, nickel; 3, aluminum; 4, manganese; 5, iron; 6, copper; 7, 
zinc; 8, lead; 9, platinum; 10, silver; 11, gold. 


CHAPTER II 


COLORING IRON AND STEEL PRODUCTS 

There are three ways in which to produce colors on metals, namely: 
First, by heat-treatment; second, by dipping in a bath; third, by 
electro-plating. Often two of these methods are used in combina¬ 
tion. A fourth might be added, that of brushing or rubbing a powder, 
or liquid, onto the piece to be colored. This is so similar to the 
dipping process, however, that it can be classed under that head. 
None of these metal-coloring processes can be learned from a few 
receipts that may be printed. Metal coloring is in reality a trade in 
itself and must be learned. 

Some of the solutions get weaker with use, and the last article 
treated will be of a different color from the first. Nearly all of the 
coloring materials have different effects on cast iron, wrought iron 
and malleable iron and will produce different shades, if not different 
colors. The chemical composition of the steels is so varied that no set 
of rules will apply to all steels. Likewise the preparation of the metal 
before coloring and the treatment given it after coloring must be 
changed to suit the kind of metal being colored. Hence it is neces¬ 
sary to know the metal that is being worked upon. It is always best 
to first experiment with a few pieces and see if uniform results are 
being obtained. It is a good rule not to treat miscellaneous steel 
pieces by the one coloring process, although some of the plating 
processes that deposit heavy coatings might be relied upon. 

Preparing- Work for Coloring 

Preparing the work for the coloring operation is of the most vital 
importance. It is absolutely necessary to remove all grease, and the 
removal of all other foreign substances for the surfaces to be colored 
is of just as much importance. In fact, only the clean metal surface 
should present itself to the coloring materials, no matter what their 
nature may be. When all the layers of oxide, grease, dirt, etc., have 
been removed the entire exposed surface can be given a uniform color 
and a quantity of pieces will be the same shade if the other conditions 
are properly looked after. 

Rust-proof Black Finish 

When a rough surface, such as is presented by castings, forgings, 
etc., is to be given the rust-proof black finish, sand blasting is the 
quickest and cheapest method of cleaning the work. In this black 
finish the metal is oxidized and coated with black magnetic oxide of 
iron. One method of producing this is to heat the work to a red heat 
in a muffle furnace in the presence of steam and hydrogen gas. A small 
amount of gasoline, injected with the steam, improves the color. The 


10 


No. 123—METAL COLORING AND FINISHING 


work should be subjected to red heat in the muffle for about an hour. 
If the work is given a thin coating of linseed oil after it has cooled 
off the color will be deepened and present a smoother appearance. 

This coating is quite hard and not easily worn away, and is a dead 
black. It is free from the red oxide that has spoiled so much work of 
this kind. The hydrogen gas is generated by passing steam over red 
hot iron chips or turnings. Cast iron, malleable iron and steel may 
all be given this black finish. The principle on which it is based is 
that of giving the surface all the oxide it will take up so that the 
oxygen in the air cannot reach it and cause corrosion. Tests have 
shown it to resist this action for many years and the color to be 
preserved. 

Black Oil Finish 

Black oil finish is produced by heating the work to a bright red; 
then quenching it in lard oil, afterward putting it back in the furnace 
to burn the oil off, and then quenching it in water. The oil must be 
kept cool and the water clean. A thin coat of linseed oil applied to 
the black gives the same results as described above. This coating is 
not durable but it will prevent rusting until the goods are sold, and 
is useful for such tools as can be heat-treated in the same operation. 

Gun-metal Finish 

Gun-metal finish is based on the same fundamental principle as 
the black finishes described above but is a great improvement over 
them and applicable to a finer class of work. For this work, as well 
as for the browns, blues or other fine colors that are produced on pol¬ 
ished surfaces, the pieces must be cleaned by methods that will not 
injure these surfaces, as does the sand blast. 

Grease and dirt are readily removed by boiling the work in a solu¬ 
tion of one pound of potash to one gallon of water. This turns the 
grease to soap, which is absorbed by the water, and the dirt falls off 
from the work. The potash will last a long time and the water can 
be replenished as it boils away. When exhausted, the bath can be 
renewed by adding fresh potash. On small work, or a few pieces, stir¬ 
ring about in benzine or paraffine will remove the grease and dirt. If 
used continuously three vessels should be provided. In the first the 
bulk of the grease would be cut from the work; in the second the bal¬ 
ance of it would be cleaned off; and the third should be kept clean 
to remove any particles that might still remain. The first two could 
contain paraffine and the third benzine. 

After this cleaning the pieces should be washed with clean water 
and thoroughly dried. If boiling water is used they will dry in the 
air; if cold water is used clean sawdust is effective for drying them. 
The work should never be touched with the bare hands as the fingers 
are likely to leave grease marks. 

Pickling- preparatory to Coloring- 

Scale, oxide, etc., are not removed by the above washing methods 
and hence a pickling in acid solutions is required. One part of sul- 


IRON AND STEEL 


11 


phuric acid to twenty parts of water is often used for iron. This mix¬ 
ture leaves the work dark colored and sometimes it has a different 
appearance at the edges. To make the work bright, the following 
pickling solution should be used: Dissolve two ounces of zinc in one 
pound of sulphuric acid and mix this with one gallon of water; then 
add one-half pound of nitric acid. The volume of the bath should be 
twenty times that of the work, to prevent it from becoming weakened 
too soon. The glassy patches on cast iron, which are usually iron sili¬ 
cate, can be removed by hydrofluoric acid. 

After pickling, the solution should be thoroughly washed off and the 
work brushed with steel scratch brushes revolving at from 600 to 1000 
R. P. M. Cleaned work can be protected from rusting by keeping it 
immersed in water containing some caustic alkali until it is needed. 
Caustic soda and sodium carbonate are both effective for this purpose. 

Polished steel surfaces can be pickled by immersing them, in con¬ 
tact with a piece of clean zinc, in a moderately strong solution of the 
acid potassium sulphate and water. Hydrogen gas is liberated when 
the zinc decomposes the solution and this removes the oxide of iron 
or rust from the steel. Another good pickling solution for steel is 
made of twenty parts hydrochloric acid and eighty parts water. Iron 
and steel can also be pickled white, in concentrated nitric acid to which 
has been added some lampblack. After pickling, the work should 
always be thoroughly washed and scratch brushed. 

Other Gun-metal Receipts and Methods 

Several different chemical solutions have been used successfully in 
giving steel the gun-metal finish or black color. Among these are the 
following: Bismuth chloride one part, copper chloride one part, 

mercury chloride two parts, hydrochloric acid six parts and water 
fifty parts. Ferric chloride one part, alcohol eight parts and water 
eight parts. Copper sulphate two parts, hydrochloric acid three parts, 
nitric acid seven parts and perchloride of iron eighty-eight parts. 
Other solutions have been prepared from nitric ether, nitric acid, 
copper sulphate, iron chloride, alcohol and water, and from nitric acid, 
copper sulphate, iron chloride and water. 

Applying these and finishing the work is practically the same in 
all cases. The surface of the work is given a very thin coating with 
a soft brush or sponge that has been well squeezed, and is then al¬ 
lowed to dry. If put on too thick the surface will be unevenly cor¬ 
roded and white spots will appear. The work is then put into a closed 
retort to which steam is admitted and maintained at a temperature 
of about 100 degrees F. until covered with a slight rust. It is then 
boiled in clean water for about fifteen minutes and allowed to dry. A 
coating of black oxide will cover the surface, and this is scratch 
brushed. After brushing, the surface will show a grayish black. By 
repeating the sponging, steaming and brushing operation several 
times a shiny black surface will be obtained that is lasting. For the 
best finishes these operations are repeated as many as eight times. 


12 


No. 123—METAL COLORING AND FINISHING 


Another process employs a solution of mercury chloride and am¬ 
monium chloride which is applied to the work three times and dried 
each time; a solution of copper sulphate, ferric chloride, nitric acid, 
alcohol and water is then applied three times and dried as before; a 
third solution of ferrous chloride, nitric acid and water, is applied 
three times and the work boiled in clean water and dried each time; 
the third and last solution of potassium chloride is then applied and the 
work boiled and dried three times. The work is then scratch brushed 
and given a thin coating of oil. Ordnance for the French Government 
was treated in this way. 

The above methods are useful for hardened and tempered steels, as 
they are only heated to about 100 degrees F. and this temperature 
does not draw the hardness. For steels that will stand GOO degrees 
temperature without losing the desired hardness, better and much 
cheaper methods have been devised. 

The color does not form a coating on the outside, as with the other 
processes, but a thin layer of the metal itself is turned to the proper 
color, which should make the color wear well. By varying the tem¬ 
perature of the furnace, the time the work is in it, and the chemical, 
different colors can be produced from the light straws to the browns, 
blues, purples and black, or gun-metal finish. Rough or sand-blasted 
surfaces will have a frosted appearance, while smooth, polished sur¬ 
faces will have a shiny brilliant appearance. 

A variety of colors can be produced on iron and steel by immersing 
the pieces, for different lengths of time, in a boiling hot solution of 
the following composition: Lead acetate fifty grains, sodium thiosul¬ 
phate fifty grains, water five fluid ounces. A half-hour immersion will 
make the work black and a shorter time will make it steel-gray, blue, 
mixed purple and blue, purple, dark brown and light brown. By con¬ 
trolling the time, the desired color can be obtained. These colors are 
very beautiful but fade quickly. A coat of lacquer on top of the color, 
liow r ever, will preserve them for years. On top of a nickel plating these 
colors are exceptionally brilliant. 

Coloring- Steel by Heat 

Producing colors on steel by heat-treatment is almost too well 
known to comment on here, and has already been referred to in the 
previous chapter. Suffice it to say that 430 degrees F. produces a 
faint yellow, 460 degrees dark yellow, 490 degrees light brown, 500 
degrees dark brown, 520 degrees light purple, 540 degrees dark purple, 
560 degrees light blue, 580 degrees dark blue, 600 degrees blue green 
and 620 degrees black. By mixing potassium nitrate and sodium 
nitrate in an iron pot and melting them, the bath can be maintained 
at any of these temperatures. By immersing the work in this bath 
until it absorbs its temperature and then cooling it, any of these colors 
can be obtained. The work can be cooled by plunging it into boiling 
water and the coating of salt removed at the same time. A thin coat¬ 
ing of these salts sticks to the steel and prevents the oxygen in the 


IRON AND STEEL 


1 Q 
lo 

air from attacking the metal and altering the color while it is being 
transferred from the nitrate bath to the boiling water. The con¬ 
tained heat will dry the work when removed from the water. 

Browning- Iron and Steel 

A good brown color can be obtained as follows: Coat the steel with 
ammonia; dry it in a warm place; then coat with muriatic or nitric 
acid; dry in a warm place; then place in a solution of tannin or gallic 
acid; and again dry. The color can be deepened by placing the work 
near the fire, but it should be withdrawn the minute the desired shade 
is reached or it will turn black. 

The U. S. Government adopted the following formula for browning 
gun barrels: Alcohol three ounces, tincture of iron three ounces, cor¬ 
rosive sublimate three ounces, sweet spirits of niter three ounces, blue 
vitriol two ounces, nitric acid one and a half ounce and warm water 
two quarts. The solution is applied with a sponge, allowed to dry for 
twenty-four hours, and after this the loose rust is removed by scratch 
brushing. A second coat is given in the same manner. After that the 
piece is boiled in water and dried quickly. A thin coat of boiled lin¬ 
seed oil or lacquer is then put on to preserve the color. 

Another process for browning iron and steel consists of dissolving 
four ounces of copper sulphate in two quarts of water and then add¬ 
ing one ounce of nitric acid, one ounce of spirits of niter, two ounces 
of alcohol and one ounce of ferric chloride. Scratch brushing and 
rubbing with a piece of smooth hard wood will polish and burnish the 
work and a coat of shellac or lacquer will preserve the color. Rub¬ 
bing with the polishing wood will give the lacquer or shellac a pol¬ 
ished surface. 

A solution that may be used in place of the above is spirits of niter 
one ounce, copper sulphate one ounce and water twenty ounces. This 
must be allowed to remain on the work for twenty-four hours and then 
brushed off with a stiff brush. The operations can be repeated 
enough times to get the depth of color desired. 

To Produce Bronze-like Color 

A warm bronze-like color can be produced by exposing iron or steel 
to the vapors of heated aqua regia, dipping them in melted vaseline, 
then heating until the vaseline begins to decompose and wiping it off 
with a soft cloth. 

Another method of producing this bronze-brown color is to slightly 
heat the work, cover the surfaces evenly with a paste of antimony 
chloride, known as “bronzing salt,” and let it stand until the desired 
color is reached. It can be made more active by adding a little nitric 
acid. 

Still another bronzing process consists of soaking the work for 
some time in an acid solution of ferric chloride, then vigorously 
moving it about in hot water and allowing it to dry, and finally brush¬ 
ing with a waxed brush. The oxygen, liberated by the decomposition 
of the water, combines with the iron and forms a dark layer of oxide. 


14 


No. 123—METAL COLORING AND FINISHING 


To Produce Gray Color 

A gray color can be obtained by immersing the work in a heated 
solution of ten grains of antimony chloride, ten grains of gallic acid, 
400 grains of ferric chloride and five fluid ounces of water. This is 
doubtless due to the antimony. The first color to appear is pale blue 
and this passes through the darker blues to the purple and finally to 
the gray. Thus if immersed long enough the metal will assume the 
gray color, but if not any of the intermediate colors may be produced. 
Used cold it is also one of the bronzing solutions. 

The Niter Process for Bluing Iron and Steel 

This process was first brought to the notice of the public in a paper 
read before the American Society of Mechanical Engineers, by Mr. 
William H. Weightman in 1886. This method produces a beautiful 
color and may, therefore, be of general interest. The process is very 
simple, the niter (nitrate of potash, often called saltpeter) is melted 
in an iron pot and heated to about 600 degrees F. The articles to be 
blued are cleaned and polished and then immersed in the molten niter, 
in which they are allowed to remain until the desired color has been 
obtained in a uniform manner. Only a few seconds are required, or, 
in general, only the length of time necessary for the articles to arrive 
at the heat of the niter. The articles are then removed and allowed 
to cool, after which they are immersed in water and the adhering 
niter washed off. Articles which will not warp or twist may be im¬ 
mersed in water immediately after having been removed from the 
niter. After the cleaning process the articles are dried in sawdust 
and then oiled with suitable oil, such as linseed, to prevent them 
from rusting. If a uniform color is to be attained continuously, a 
pyrometer should be used to control the temperature of the heated 
niter, because a higher heat than 600 degrees F. will produce a dark 
color, while a lower heat will make the objects light. 

The niter process can scarcely be called suitable for small articles 
on account of its cost. Niter itself is not expensive, but the pieces 
must be dipped carefully in order to obtain the desired color and 
the handling in washing them off afterwards and drying them makes 
the cost per piece high. It is, therefore, used mostly for medium¬ 
sized and large work. 

Mottling 

The mottled colors can be produced by heating the steel pieces to 
a good cherry red for several minutes in cyanide of potassium, then 
pouring the cyanide off and placing the pot of work back in the fire 
for five minutes and then quickly dumping the contents into clean 
water. To heighten the colors the work should afterward be well 
boiled in water and oiled while hot. This also carbonizes the work 
and larger lots could be handled in the regular carbonizing furnaces. 


CHAPTER III 


COLORING NON-FERROUS METALS AND ALLOYS 

In thickly inhabited sections a great deal of coal gas is burned. 
More or less of the products of combustion, together with the gases 
arising from the manufacture of other materials, stay in the atmos¬ 
phere and give to brass and bronze objects a dark, dirty color by 
attacking their surfaces. The oxygen and moisture in the atmosphere 
also give these metals or alloys a disagreeable color. Hence coloring 
or coating is also resorted to for the purpose of enhancing and pre¬ 
serving the original beauty of the metal. Sometimes rich and beauti¬ 
ful browns and greens are produced on copper alloys that have been 
subjected to atmospheric conditions for years. Therefore these con¬ 
ditions have been studied and chemical means have been found for 
producing the colors quickly and on a commercial scale. 

Copper is more susceptible to coloring processes than any of the 
other metals, and hence the alloys containing large percentages of 
copper are readily given various shades of the yellow, brown, red, 
blue and purple colors and also black. Alloys with smaller percentages 
of copper, or none at all, can be given various colors, but not as 
easily as if copper were the principal ingredient, and the higher 
the copper content, the more readily can the alloy be colored. The 
shades, and even the colors, can be altered by varying the density 
of the solution, its temperature and the length of time the object is 
immersed. They can also be altered by finishing the work in dif¬ 
ferent ways. If a cotton buff is used one shade will be produced; 
a scratch brush will produce another, etc. Thus to color work the 
same shade as that of a former lot all the data in connection with 
these operations must be preserved so they can be repeated with 
exactness. 

Many different kinds of salts are made into solutions for the coloring 
processes. When capable of producing the desired results it is always 
best to use the simple salts. It is often necessary to combine two or 
more salts in the solution to get the required color, but these de¬ 
teriorate in strength much more rapidly than the simple salt solu¬ 
tions and hence the last piece immersed will have a lighter color than 
the first one. When adding salts to bring back the original strength 
of the bath, they should first be dissolved in a small amount of water 
to prevent their settling to the bottom where they might become 
covered with an insoluble mud that would prevent them from being 
dissolved. In making the solutions it should be remembered that 
a strong solution will produce the color quickly and a weak solution 
more slowly. When a uniform coating can be produced the strong 
solution is always the best owing to the time factor. The most ef¬ 
fective and lasting results, however, are obtained with the weaker 


1G 


No. 123—METAL COLORING AND FINISHING 


solutions, and hence they are used for high-grade work. While these 
solutions are often used cold, there are many cases where better 
results can he obtained when they are heated. Raising the bath to 
the boiling point will insure a complete solubility of the salt. 

Cleaning- Work to be Colored 

Cleaning the work is of the utmost importance before attempting 
to give it any kind of color. A greenish or brownish film forms 
on copper, brass, bronze, etc., when they stand, as they are attacked 
by the moisture in the air and the simultaneous presence of carbonic 
acid which gradually changes into carbonates. This film is a mixture 
of carbonate of copper and oxide. Often sulphur compounds are 
formed when the atmosphere is impregnated with the products of 
combustion arising from the coal gas burned in cities and towns. 
This is nearly always stronger in rooms than in the open. If these, 
films are not removed before coloring they show up as stains and 
the work will be streaked or spotted. Touching the work with the 
bare hands after it is cleaned will also leave a slight film that will 
make the work spotted, and hence it should be strung on wires or 
handled in other ways that will prevent it from being touched with 
the hands. 

Several acid dips can be made that will remove these films and 
leave the bright clean metal with its original smooth surface. Work 
that will stand heating can be heated to a dull red and then plunged 
into dilute sulphuric acid, after which it should be soaked in old 
aquafortis and then thoroughly rinsed. It should be soaked long 
enough to have a uniform metallic appearance, and the bath should be 
large enough in volume to prevent its heating up from the hot work. 
The best results are obtained with straw-colored aquafortis, as the 
white is too weak and the red too strong. In diluting the sulphuric 
acid it should always be poured into the water slowly, as heat is gen¬ 
erated, and too rapid mixing generates so much heat that the con¬ 
taining vessel is liable to crack and the escaping liquid to cause burns. 
To pour water into sulphuric acid will cause an explosion that is almost 
sure to result in serious, if not fatal, burns from the flying liquid. 

A good method of removing these films, without heat, is to soak the 
work in a pickle composed of spent aquafortis until a black scale is 
formed and then dip it for a few minutes into a solution composed 
of G4 parts water, 64 parts commercial sulphuric acid, 32 parts aqua¬ 
fortis and 1 part hydrochloric acid. After that the work should be 
thoroughly rinsed several times with distilled water. If the strong 
aquafortis is used for the pickle in which the work is soaked it will 
cause a too rapid corrosion of the copper during the time of the 
solution of the protoxide. Hence the spent aquafortis is better on 
account of its slower action and it also saves the cost of new. A dip 
that is useful for removing the sand, etc., that sticks to castings is 
composed of 1 part spent aquafortis, 2 parts water and 6 parts 
hydrochloric acid. A few minutes will suffice for small pieces, but 


NON-FERROUS METALS 


17 


large castings can remain in the hath for thirty minutes. They 
become coated with a black mud and when this is thoroughly washed 
off they should be bright. 

If a further whitening of the work is desired a solution may be 
made by mixing 3 pounds nitric acid, 4 pounds sulphuric acid and 
40 grains sodium chloride (table salt), combining this with 40 times 
its bulk of water and allowing it to cool before using. If a dead 
surface is desired the following mixture can be added to the bath: 
2 pounds nitric acid, 1 pound sulphuric acid, 10 grains sodium chloride 
and 40 grains zinc sulphate. The degree of deadness is determined 
by the length of time the work is left in the bath. As with all other 
solutions, the work should be well rinsed after leaving the bath and 
then thoroughly dried. Another dead dipping bath can be made from 
one part of a concentrated solution of potassium bichromate and two 
parts of concentrated hydrochloric acid. Many other combinations of 
chemicals may also be made for cleaning or whitening the work or 
giving a dead finish after it has been colored, but those given above 
will suffice for the present. 

Bright Castings 

The bright clean color sometimes seen on bronze castings has been 
thought by many to be the result of an acid dip. This has been 
produced, however, by plunging the castings into water while they 
are still red-hot. It is seldom that brass castings can be given this 
color as they usually contain too much lead. Likewise the bronze 
castings must be free from lead as well as iron, antimony or other 
impurities, and the water into which they are plunged must be clean, 
or a dirty, unpleasant color will be the result. The castings must 
also be as hot as possible when quenched. If too hot the metal will 
be brittle and hence the highness of the temperature is governed by 
the toughness that is desired in the casting, but if quenched after 
they have cooled too much the color will be dull. Copper ingots can 
be given a beautiful rose-red color by this method. 

To Produce Yellow to Orange Colors 

Polished brass pieces can be given a color from a golden yellow to an 
orange, by immersing them for the correct length of time in a solu¬ 
tion composed ©f 5 parts caustic soda to 50 parts w r ater, by weight, and 
10 parts copper carbonate. When the desired shade is reached the 
work must be well washed with water and dried in sawdust. Golden 
yellow may be produced with the following: Dissolve 100 grains lead 
acetate in 1 pint water and add a solution of sodium hydrate until 
the precipitate which first forms is redissolved, and then add 300 
grains red potassium ferri-cyanide. With the solution at ordinary 
temperatures the work will assume a golden yellow, but .heating the 
solution darkens the color until at 125 degrees F. it has changed to 
a brown. A pale copper color can be given brass by heating it over 
a charcoal fire, with no smoke, until it turns a blackish brown, then 
immersing in a solution of zinc chloride that is gently boiling, and 


18 


No. 123—METAL COLORING AND FINISHING 


finally washing thoroughly in water. Dark yellow can he obtained 
by immersing for five minutes in a saturated solution of common 
salt containing some free hydrochloric acid and which has as much 
ammonium sulphide added as the solution will dissolve. 

To Produce a Rich Gold Color 

A rich gold color can be given brass by boiling it in a solution 
composed of 2 parts saltpeter, 1 part common salt, 1 part alum, 24 
parts water, by weight, and 1 part hydrochloric acid. Another method 
is to apply to the work a mixture of 3 parts alum, 6 parts saltpeter, 
3 parts sulphate of zinc and 3 parts common salt. The work is then 
heated over a hot plate until it becomes black and then washed with 
water, rubbed with vinegar and again washed and dried. Still another 
solution is made by dissolving 150 grains sodium thiosulphate in 300 
grains water and adding 100 grains of an antimony chloride solution. 
After boiling for some time the red-colored precipitate must be filtered 
off, well washed with water and added to 4 pints of hot water. Then 
add a saturated solution of sodium hydrate and heat until the pre¬ 
cipitate is dissolved. Immerse the brass articles in the latter solu¬ 
tion until they have attained the correct shade. If left in too long 
they will be given a gray color. 

To Produce White Colors or Coatings 

The white color or coating that is given to such brass articles as 
pins, hooks and eyes, buttons, etc., can be produced by dipping them 
in a solution that is made up as follows: Dissolve 2 ounces fine grain 
silver in nitric acid, then add 1 gallon distilled water and put into 
a strong solution of sodium chloride. The silver will precipitate in 
the form of chloride and this must be washed until all traces of acid 
are removed. Testing the last rinse water with litmus paper will 
show when the acid has disappeared. Then mix this chloride of 
silver with an equal amount of potassium bitartrate (cream of tartar) 
and add enough water to give it the consistency of cream. The work 
is then immersed in this and stirred around until properly coated, 
after which it is rinsed in hot water and dried in sawdust. 

Silvering 

Another method of silvering that is applicable to such work as gage 
or clock dials, etc., consists of grinding together in a mortar 1 ounce 
very dry chloride of silver, 2 ounces cream of tartar and 3 ounces 
common salt. Then add enough water to make it of the desired con¬ 
sistency and rub it on the work with a soft cloth. This will give 
brass or bronze surfaces a dead white thin silver coating, but it will 
tarnish and wear if not given a coat of lacquer. The ordinary silver 
lacquers that can be applied cold are the best. The mixture as it 
leaves' the mortar, before adding the water, can be kept a long time 
if put in very dark colored bottles, but if left where it will be attacked 
by light it will decompose. 


NON-FERROUS METALS 


19 


Assorted Colors 

Some very interesting results in coloring brass can be obtained 
by dissolving 200 grains sodium thiosulphate and 200 grains lead 
acetate in 1 pint water and heating it to from 190 to 195 degrees F. 
Immersing the work in this for five seconds will make it pale gold; 
fifteen seconds, brown gold; twenty-five seconds, crimson; thirty sec¬ 
onds, purple; forty-five seconds, an iridescent bluish crimson green; 
sixty seconds, pale blue; sixty-five seconds, mottled purple; eighty 
seconds, nickel color; eighty-five seconds, mottled blue and pink; 
one hundred and ten seconds; mottled purple and yellow; two and 
one-half minutes, pale purple; four minutes, mottled pink and yel¬ 
low; five minutes, mottled gray; ten minutes, mottled pink and light 
blue. Other combinations of colors can also be obtained, but some 
of these fade and change color unless protected by a coat of lacquer. 
By using one-quarter ounce of sulphuric acid in place of the lead 
acetate a variety of colors can also be produced, but they will not be 
as good a quality as those made with the above solution. Nitrate 
of iron can also be used. 

To Produce Gray Colors 

A solution of 1 ounce of arsenic chloride in 1 pint of water will pro¬ 
duce a gray color on brass, but if the work is left in too long it will 
become black. The brass objects are left in the bath until they have 
assumed the correct shade and then are washed in clean warm water, 
dried in sawdust and finally in warm air. A dark gray color that 
can be made lighter by scratch brushing can be obtained by immers¬ 
ing the work in the following solution: 2 ounces white arsenic oxide, 
4 ounces commercially pure (c. p.) hydrochloric acid, 1 ounce sul¬ 
phuric acid and 24 ounces water. A steel gray can be produced with 
the following: 20 ounces arsenious oxide, 10 ounces powdered copper 
sulphate, 2 ounces ammonium chloride and 1 gallon hydrochloric acid. 
After mixing, this should stand for one day. A 5 per cent solution of 
platinum chloride in 95 per cent water will also produce a dark gray 
color if it is painted on and the brass is warmed. Weaker solutions 
will make the color lighter. Copper can also be colored, but the 
platinum does not adhere as firmly to the surface as it does on brass. 
A coating of lacquer is required to make it permanent. By smearing 
the work with a mixture of 1 part copper sulphate and 1 part zinc 
chloride in 2 parts water and drying this mixture on the brass, with 
heat, a dark brownish color is obtained. If desirous of immersing the 
work a weaker solution could be used. The color is changed very 
little by exposure to light. 

To Produce Lilac Blue and Violet Colors 

The lilac shades can be produced on yellow brass by immersing the 
work in the following solution when heated to between 160 and 180 
degrees F. Thoroughly mix 1 ounce chloride, or butter, of antimony 
in 2 quarts muriatic acid, and then add 1 gallon water. 

To give brass a blue color dissolve 1 ounce antimony chloride in 20 
ounces water, and add 3 ounces hydrochloric acid. Then warm the 


20 


No. 123—METAL COLORING AND FINISHING 


work and immerse it in this solution until the desired blue is obtained. 
After that, wash it in clean water and dry in sawdust. A permanent 
and beautiful blue-black can be obtained by using just enough water 
to dissolve 2 ounces copper sulphate and then adding enough am¬ 
monia to neutralize and make it slightly alkaline. The work must 
be heated before immersion. Copper nitrate, water and ammonia will 
also yield this rich blue-black, but if the brass is very highly heated 
after immersion it changes to a dull steely black. On copper or work 
that is copper-plated this latter produces a crimson color. 

A beautiful violet color can be produced on polished brass with a 
mixture of two solutions. First, 4 ounces sodium hyposulphite is dis¬ 
solved in 1 quart water, then 1 ounce sugar of lead is dissolved in an¬ 
other quart of water and the two are well stirred together. By heat¬ 
ing this to 175 degrees F. and immersing the work the correct length 
of time, it takes on the violet color. The work first turns a golden 
yellow and this gradually turns to violet. If left a longer time the 
violet will turn to blue and then to green. Thus this same prepara¬ 
tion can be used for all of these colors by correctly limiting the time 
that the work is immersed. 

To Produce Green Colors 

When left to the natural action of the atmosphere, or ageing, most 
of the brasses and bronzes first turn green, and very decidedly so if 
near the ocean where the moisture from the salt water attacks the 
metal. This green color gradually darkens and then turns brown 
and finally black. Some of the shades it assumes are very beautiful 
and hence they have been produced by chemical means, as nature is 
too slow in its action. So many different chemical combinations are 
used for this purpose that it would require a book to enumerate them 
all and hence only a few can be mentioned. Some of the green colors 
can be produced by the solutions given above, but the antique, or rust, 
greens require different mixtures. 

One solution that will produce the verde antique, or rust green, is 
composed of 3 ounces crystallized chloride of iron, 1 pound ammonium 
chloride, 8 ounces verdigris, 10 ounces common salt, 4 ounces potas¬ 
sium bitartrate and 1 gallon water. If the objects to be colored are 
large, this can be put on with a brush and several applications may be 
required to give the desired depth of color. Small work should be 
immersed and the length of time it is immersed will govern the light¬ 
ness or darkness of the color. After immersion, stippling the surface 
with a soft round brush, dampened with the solution, will give it the 
variegated appearance of the naturally aged brass or bronze. Another 
solution that will give practically the same results is composed of 2 
ounces ammonium chloride, 2 ounces common salt, 4 ounces aqua- 
ammonia and 1 gallon water. The work may have to be immersed or 
painted several times to give it the desired coating, and after washing 
and drying it should be lacquered or waxed. The Flemish finish can 
be given brass with a solution composed of % ounce sulphuret of 
potassium, 1 to 2 ounces white arsenic, 1 quart muriatic acid and 10 


NON-FERROUS METALS 


21 


gallons of water. The arsenic should be dissolved in a part of the 
acid by heating and then mixed with the balance of the acid and 
water. Two ounces sulphuret of potassium in a gallon of water may 
also be used if it is heated to 160 degrees F. One ounce sulphuric or 
muriatic acid in a gallon of water darkens the color produced by this 
last mixture. 

To Produce Brown Colors 

Many different shades of brown can be produced and many different 
chemicals are used to form solutions or pastes for this purpose. In 
these liver of sulphur, either potassium sulphide or sodium sulphide, 
is one of the most commonly used chemicals. One-fourth ounce liver 
of sulphur in 1 gallon water will give bronze a brown color when used 
cold but if heated it is more effective. The depth of the color is gov¬ 
erned by the length of time that the work is immersed. If left in too 
long, however, it becomes black and if too much liver of sulphur is 
used the color will be black. Copper is turned black even with the 
weak solutions. To set the color it should afterwards be immersed in 
water containing a small amount of sulphuric or nitric acid. Brass 
is not attacked by this solution but if caustic potash is added it causes 
the liver of sulphur to color the brass. Then 2 ounces liver of sulphur 
should be added to 1 gallon water and from 2 to 8 ounces caustic 
potash, according to the shade of brown that is desired; the more 
potash the darker will be the color. A solution composed of % 
ounce potassium sulphide in 1 gallon of water will produce a gray or 
greenish color on brass when cold but when heated to 100 degrees F. 
it produces a light brown; at 120 degrees, a reddish brown; at 140 
degrees, a dark brown; and at 180 degrees, a black color. 

The barbedienne bronze, or brown, color can be produced on cast 
brass or bronze by immersing in a solution made by dissolving 2 
ounces golden sulphuret of antimony and 8 ounces caustic soda in 1 
gallon water. The work must be properly cleaned beforehand and 
afterwards scratch-brushed wet, with a little pumice stone applied 
when brushing. It must then be well washed and dried in sawdust. 
A second immersion in a solution of one-half the above strength will 
have a toning effect, and the work must again be washed and dried. 
The high light can be made to show relief by rubbing the object with 
pumice stone paste on a soft rag. A dead effect can be produced by 
immersing in a hot sulphuret of antimony solution for ten or fifteen 
seconds, then rewashing and immersing in hot water for a few seconds 
and drying in sawdust. The work should be lacquered to preserve the 
tones and waxed when the lacquer has become dry and hard. This 
brown color can be darkened by a five-seconds immersion in a cold solu¬ 
tion of 8 ounces sulphate of copper in 1 gallon water. Some other 
processes use two solutions, the first of which is heated and the second 
used cold, after which the work is rinsed in boiling water. 

. To Produce Black 

There are as many different processes and solutions for blackening 
brass as there are for browning, and consequently only a few can be 


22 No. 123—METAL COLORING AND FINISHING 

given. Trioxide of arsenic, white arsenic or arsenious acid are dif¬ 
ferent names for the chemical that is most commonly used. Its use 
can be traced back to the fifth century and it is the cheapest chemical 
for producing black on brass, copper, nickel, German silver, etc. It 
has a tendency to fade and a much greater tendency if not properly 
applied, but a coat of lacquer will preserve it a long time. A good 
black can be produced by immersing work in a solution composed of 2 
ounces white arsenic and 5 ounces cyanide of potassium in 1 gallon 
water. This should be boiled on a gas stove, in an enamel or agate 
vessel and used hot. Another cheap solution is composed of 8 ounces 
sugar of lead, 8 ounces hyposulphite of soda and 1 gallon water. This 
must also be used hot and the work afterwards lacquered to prevent 
fading. When immersed the brass first turns yellow, then blue and 
then black, the latter being a deposit of sulphide of lead. 

The ammonia-copper carbonate solution much used for medals, orna¬ 
ments, etc., is made by taking the desired quantity of the strongest 
ammonia water and mixing it with an equal amount of distilled water, 
and dissolving carbonate of copper in it until it is thoroughly satur¬ 
ated and a little remains undissolved. This is placed in a stone crock 
and surrounded with water and then heated to from 150 to 170 de¬ 
grees F. before the work is immersed. After immersing for a few 
seconds the brass will turn black; it is then removed, rinsed in cold 
water, dried, and given a coat of dead, black lacquer. 

“Heat-Black” Finish on Brass, Bronze and Copper 

The so-called “heat-black” finish on brass, copper, or bronze is one 
of the new methods of coloring metals that has recently appeared and 
is one of the most durable. It is adapted for a large variety of work 
and is even replacing nickel-plated work for some kinds of articles. 
Desk telephone sets are now being finished in the “heat-black,” and in 
many parts of the United States have supplanted the nickel-plated 
article previously used. 

The adaptability of the “heat-black” finish is wide, and the reader 
will undoubtedly find many new uses for it. The color is an absolute 
dead black, and as it is not difficult to apply, the future will undoubt¬ 
edly find it extensively employed. It can be applied to brass, bronze 
or copper. It does not work evenly on steel or iron. 

The article to be treated should be free from grease, although a slight 
tarnish does no harm. It is usually customary to sand blast the sur¬ 
face, although very good results may be produced without it. A sand¬ 
blasted surface takes an excellent finish, but those who do not possess 
the apparatus for producing it need not have any hesitation in using 
the finish without it, as about the only difference between the results 
is that the sand-blasted surface is a little more dead. 

Two stock solutions are first made up. One is a solution of nitrate 
of copper in water, and the other is a solution of nitrate of silver in 
water. The proportions need not be exact, although it is preferable 
to keep them fairly close. According to the Brass World , they are 
made up as follows: 


NON-FERROUS METALS 23 

Nitrate of Copper Solution 

Water . 1 oz. 

Nitrate of copper.. 1 oz. 


This gives a practically saturated solution of nitrate of copper in 
water and is used for a “stock” solution. If desired, the nitrate of 
copper may easily be made by taking 1 ounce of strong nitric acid and 
dissolving in it all the copper wire it will take up. A thick, blue solu¬ 
tion is left which is used for the “stock” solution. As few platers 
have nitrate of copper in stock, it can easily be made from the copper 
wire. 

* 

Nitrate of Silver Solution 


Water . 1 oz. 

Nitrate of silver. 1 oz. 


This solution can also be made by dissolving pure silver in nitric 
acid until no more will dissolve, but dilute acid (1 part acid and 1 
part of water) should be used as silver does not dissolve readily in 
strong nitric acid. It is preferable, however, to purchase the nitrate of 
silver as it is easily obtained. The nitrate of silver solution is prac¬ 
tically a saturated solution and is used as the “stock” solution. 

Mixed Solution for Applying- 

The mixed solution for applying to the metal is made as follows: 


Water . 3 parts 

Nitrate of copper solution. 2 parts 

Nitrate of silver solution. 1 part 


The solution is kept in a glass or stone-ware vessel for use. 

Applying- to Brass or Other Metals 

The brass, bronze or copper article to be treated is heated on a hot 
iron plate or in an oven to a temperature of about 250 degrees F. and 
the solution applied with a brush or cotton swab so as to cover the 
surface uniformly. The brush should be a rather soft one in order 
to allow the coating to be made in the best manner. The so-called 
“rubber-set” brushes are the best for the purpose, as there is no metal 
on them to be attacked by the solution. 

One or two coatings of the solution on the surface of the article is 
usually enough; it dries almost immediately leaving a green froth. 
The temperature is not sufficiently high to draw the temper of hard 
brass, but it will usually melt soft solder. 

When the entire surface has changed to a uniform black color, allow 
the article to cool and then brush off the fluffy material on the surface 
of the metal with a stiff-bristled brush. The color will now change to 
a brownish-black that is quite pleasing for many purposes and which is 
very tenacious. When the fluffy material is completely brushed off, 
it is surprising how even and uniform the coating is and how tena- 
{-jjQugly r adheres. If the brown-black finish is desired, the sui face 
may now be waxed or lacquered, but it is usually customary to give 









24 


No. 123—METAL COLORING AND FINISHING 


the article an additional treatment in a liver of sulphur solution in 
order to change the brown-black coating to one that is absolutely dead 
black. 

Final Treatment 

When the smut has been brushed off from the surface of the article, 
it is immersed in a cold liver of sulphur solution for 5 minutes. This 
solution is made by dissolving 2 ounces of liver of sulphur in 1 gallon 
of water. The article is immersed in it, allowed to remain about 5 
minutes and then, without rinsing, is again heated until the surface 
is uniformly black. 

The surface is now brushed again with the bristle brush when it will 
be found that the color is a dead black and quite uniform. It should 
be borne in mind that the article is not rinsed at all after it is removed 
from the liver of sulphur solution, but is simply drained off and then 
heated. 

The article may now be lacquered with a flat lacquer or waxed as 
may be desired. The final appearance of the surface will be found 
quite satisfactory and contrary to what one would naturally expect. 
The coating of the solution that is first applied need not be very even 
as long as a sufficient quantity is put on. 

The process as arranged by steps may be summed up as follows: 

1. Applying the solution to the metal. 

2. Heating on a hot plate or oven until the solution has dried and 
the residue left by evaporation has turned black. 

3. Brushing off the smut. 

4. Immersion for about 5 minutes in a liver of sulphur solution. 

5. Drying without rinsing and heating on the plate or in the 
oven again. 

6. Lacquering or waxing. 

If the surface is not satisfactory, or an old article is to be refinished, 
the wax or lacquer may be burned off and the process repeated. 

It is believed that this is one of the most satisfactory black finishes 
known, as it is dead black, is readily applied and is very durable. 
It is calculated to resist considerable handling, such as a desk tele¬ 
phone would receive. There are many articles that can well be treated 
by it. 

Oxidizing 

Solutions that produce the green, brown or black colors are usually 
used when it is desired to oxidize copper, brass or bronze. A dark 
slate green can be produced with a solution composed of 8 ounces 
double nickel salts, 8 ounces sodium hyposulphite and 1 gallon water. 
The color is almost instantly produced when the temperature of the 
solution is above 150 degrees F., but below the boiling point, and the 
articles immersed. After removing and rinsing in water the relief is 
easily produced with pumice stone or other abrasives. This green 
color harmonizes well with the metal color. 


NON-FERROUS METALS 


The browns and blacks are coated on the metal in the same manner 
as described under these headings; those solutions that are used 
hot give the best results, as the coating is more tenacious and better 
withstands the buffing that is necessary when oxidizing the work. 
Many beautiful effects are produced by these combinations of colors, 
and while it is not difficult to relieve the rough surfaces of cast, 
stamped or pressed articles it requires considerable skill to properly 
relieve turned or polished surfaces. 

Mottling- 

I 

After properly buffing and cleaning the work, a handsome mottled 
effect can be produced by first immersing it in a boiling solution com¬ 
posed of 8 ounces sulphate of copper, 2 ounces sal-ammoniac and 1 
gallon water. This produces a light taffy color that soon changes to 
an olive green. The work should be removed when the taffy color ap¬ 
pears and dipped in a second solution composed of 4 ounces sal-soda in 
1 gallon water and that has the surface covered with a small amount 
of lard oil or gasoline. After that the work is again immersed in the 
first solution until the olive-green color is produced. The oil spreads 
over the surface and prevents the uniform action of the first solution, 
and hence the taffy and olive-green colors are mottled together with 
a pleasing effect. The same process might be used with different 
chemical solutions to mottle work with other combinations of colors. 

Coloring Aluminum 

Aluminum is the most difficult of metals to color. Heretofore alum¬ 
inum parts have only been colored by coating them with lacquers of 
different colors, but a process has recently been patented by Salamon 
Axelrod in Germany that produces different metallic colors. Either 
a neutral or alkaline cobaltous nitrate is made into a water solution 
into which the articles are dipped, or it may be painted on pieces too 
large to dip. After that the work is heated and the degree of heat 
determines the color. A low temperature produces a steel gray 
color that changes to brown with a higher heat and to a durable and 
permanent dead black when the temperature is still higher. Zinc, 
tin and other white metals may also be colored with similar cobalt 
salt solutions. 

The gun-metal finish can be given aluminum by immersing it for 
from six to ten seconds in a cold solution of 12 parts hydrochloric acid, 
1 part chloride of antimony and 87 parts distilled water. After that, 
thoroughly wash it in running water for several minutes, dry with 
heat and lightly buff with a high-speed wheel. The color penetrates 
the metal and its depth is governed by the length of time it is im¬ 
mersed. If immersed longer than ten seconds the solution should be 
weakened, as hydrochloric acid eats the metal. 

Nearly any color can be plated on any of the metals or alloys by 
electro deposition, but this is an art or trade that requires experi¬ 
enced platers. Electrochroma is the name given a new plating pro¬ 
cess that promises to revolutionize the older methods of plating on 


26 


No. 123—METAL COLORING AND FINISHING 


colors. It produces any desired shade of green, blue, red, violet or 
yellow and black and white by immersion in the electrolyte for from 
one-half minute to two minutes. The work is made the cathode. One 
of its special features is the coloring of leaded glass. The lead can be 
given any desired color, while the glass is not affected but is left clean 
and with a clear luster. Heretofore the lead has been painted by hand, 
which is a long, tedious job, often consuming a day or more for one 
piece. It is also easy to match colors with this plating process and 
they are permanent enough not to require lacquering or waxing. The 
plating processes, however, are separate and distinct from those given 
above, as these do not require an electric current nor the high degree 
of knowledge and skill that goes with the plater’s profession. 


CHAPTER IV 


LATHE BURNISHING OP METALS 

The burnishing of metals while not requiring the skill of the spinner, 
or the multiple operations or tools used in that craft, still is a trade 
that is separate and distinct from spinning. Metal burnishing can be 
divided into three classes: 

1. Hand burnishing of irregular shapes, such as tableware, jewelry, 
belt buckles, metal clocks, ornaments and all metal parts that cannot 
be revolved on the lathe, using steel hand tools of various shapes. 

2. The burnishing of small round work in the lathe, such as but¬ 
tons, ornaments, etc.—mostly plated ware that has already been sur¬ 
faced and is operated on to brighten only—not requiring the heavy 
pressure of the tool, and being mostly done with blood-stone bur¬ 
nishers, a natural stone of small size mounted in a steel holder. These 
stones, some of which are very expensive, last for years. 

3. The burnishing of unfinished or rough work in the lathe, which 
requires smoothing and polishing at the same time; this requires con¬ 
siderable pressure. The blood-stone burnisher would be ruined on 
this class of work. The tools used are of steel and the handles are 
short; they are held in the hand only. A strong wrist and muscular 
arm are required for burnishing, as well as a steady feed of the tool, 
which is partly accomplished by the movement of the body, in con¬ 
junction with the arm and wrist motion; the hand is steadied by 
being held against the body. 

Burnishing may be described as an economical way to finish, polish 
or brighten the surface of metal, without wasting any of the material. 
It is also a means of strengthening the metal by tempering or harden- 


BURNISHING 


27 


mg it; this is accomplished by pushing the tool over the work, be¬ 
ginning at the front end and pushing always against the chuck. The 
toolpost is used as a fulcrum and the tool, which is pressed against the 
work, as a lever. The tool is given a slight rotary motion, and only 
the thin edge or end is used. 

While the pressure against the work does not seem great, still the 
area in contact with metal is so small, and the speed of the lathe so 
high, being from 3200 to 5000 revolutions per minute, that the tool 
leaves a bright mark. The skill of the operator lies in passing the 
tool over the metal so as to leave a continuous bright surface without 



Fig. 1. View showing Method of Moistening Work with Finger Pads and 
also Position and Angle of Burnishing Tool 


any trace of the tool marks; to do this the tool must be fed with 
regularity and without overlapping or leaving any dull places. 

After sheet metal is spun, or drawn in presses, the smooth, even 
surface which it has when it comes from the mills is changed to a 
rough, uneven surface having high and low spots which are hardly 
noticeable to the naked eye, but very easily distinguished under the 
magnifying glass. The working operations distend or elongate the 
molecules, and the annealing operation restores them to their original 
shape. Some shells are annealed several times before the burnishing 
operation is reached, besides being pickled after each annealing to 
remove the scale; this leaves the surface of the metal in a pebbly or 
matted condition, as well as soft and without temper. 

A spun shell can be gone over with a planisher, and hardened, but 
the scale and dirt is crowded into the grain of the metal, and the 
only way to get a smooth surface is to buff or cut it down until this 
pitted face is removed thus wasting about 10 per cent of the metal. 







28 


No. 123—METAL COLORING AND FINISHING 


Tlie spinner can do this in another way, that is by skimming or 
shaving the uneven surface, but even more metal is wasted than by 
buffing, and the shell is also weakened by gouging the high places. 
This same shell could be left without polish, and the chuck transferred 
to the burnishing lathe, which runs at much greater speed than one 
used for spinning. After the shell is dipped bright to remove all 
spinning dirt and scale, it can then be polished to an even surface, the 
uneven face of the metal being amalgamated or smoothed down to a 
bright surface of the proper temper; it is then colored with a cloth 
buff to obtain a perfect finish. The gage or thickness remains the 
same as there is no dirt or scale to buff out. 

Burnishing is economical, especially on pressed or drawn work 
made in large quantities, some work being finished at the rate of five 



Fig. 2. Burnishing Lathe Equipped with Split Chuck 


hundred or more an hour. It is necessary to have a metal chuck in 
burnishing, and where the shell has been spun on such a chuck, the 
latter can be used for both operations. Some work can be lacquered 
without coloring on the buff wheel, the only operation after burnish¬ 
ing being to wash in hot water and dry at once in hot sawdust. 

A burnishing lathe is smaller than a spinning lathe, and it has only 
one speed. The countershaft is fastened to the floor under the lathe; 
this is necessary on account of the great speed, besides a down-pull of 
the driving belt causes less vibration than the up-pull of a belt from an 
overhead countershaft. The speed of burnishing lathes is varied for 
different classes of work. In a group of four lathes in use in one fac¬ 
tory one is belted to run at 5000 revolutions, two at 4000 revolutions and 
one at 3200 revolutions a minute. Lathes for very large work of 12 
inches and over in diameter have straight babbitted bearings, with 
a back screw and button to take up the end shake. The babbitt has to 
be renewed about once a year for continuous service, only the best 
grade being used. All threads on the spindles are of one standard size, 
the chucks being interchangeable for the burnishing and spinning 
lathes. 









BURNISHING 


29 


In some shops it is customary to have a small stream of water run¬ 
ning on the work above the chuck, the connections being hinged, so 
that the stream can be guided above the tool. A back center is used 
to hold the work against the chuck. The operator wears a rubber 
apron to protect himself from the flying water, and stands in a shallow 
trough that has a drain. The great speed of the lathe throws off all 
surplus water, leaving only a thin film next to the metal—all that is 
necessary. 

This chapter describes a method of burnishing that is used in many 
shops. The shells are first dipped in a tank of water, which is on the 
bench back of the lathe head; they are then held on the chuck by the 
left hand, the thumb and first three fingers being covered with canvas 
pads. These pads are dipped in the water and are held opposite the 
burnishing tool and slightly in advance of it to keep the metal moist, 



Fig. 3. Burnishing Lathe Steady-rests and Finger Pads 


thus leaving no surplus of water to be thrown off. The hand also 
holds the work against the chuck instead of the back center. Some¬ 
times on large work it is necessary to dip the pads in the water a 
second time; also where a very fine polish is wanted it is necessary 
to pass the tool over the work twice, roughing it down on the first 
pass and finishing it on the second, using the same tool without taking 
it off the chuck. 

Fig. 1 shows the method of using the pads on the fingers and also 
the proper position and angle of the tool, as well as the height of tool- 
post or rest. The chuck shown is Sy 2 inches in diameter and weighs 
36 pounds; it runs at 4000 revolutions per minute. The shell has been 
gone over twice. 

Fig. 2 shows a burnishing lathe equipped with a split chuck, one 
part being in the tail-spindle and having a roller end bearing. All 
chucks for burnishing are like the spinning chucks, except that 
greater care must be taken in machining them to have them perfectly 
balanced. 

Fig. 3 is a view of the steady-rests that are used on burnishing 
lathes. These are different from the spinning rests, for while the 
spinner uses only one pin as a fulcrum, changing it from one hole to 





30 


No. 123—METAL COLORING AND FINISHING 


another as the work advances, the burnisher uses several pins of much 
smaller size, inserting as many pins as he needs positions for the sweep 
of his tool. These pins are about % inch to 9/32 inch in diameter and 
are tapered 2% degrees on the end which is inserted in the cross-bar ) 
of the steady-rest, the holes also being tapered and the pins driven 
in tight. The canvas finger cots that are used on the left hand to 
moisten the work are shown at A. 

Fig. 4 shows a group of burnishing tools, some of which are of 
high speed steel, and others of regular tool steel. These tools are 
made extremely hard and no temper is drawn. They project out of 
the handles from 2 y 2 to 5 inches and are %, 7/16, y 2 , and % inch in 



Fig. 4. Group of Tools used for Burnishing 

diameter. The round tools A are used on heavy work; also to get in 
sharp corners and to burnish shells which are part plain and part 
embossed, requiring the tool to be lifted from one part of the work 
to another to avoid the embossed area. B is a flat tool with a slight 
curve on the end; it is used mostly on straight work and convex sur¬ 
faces. G is a flat tool with a greater curve on the end, and it is used 
mostly on concave surfaces, while D is a flat tool with a still greater 
curve on the end, for use on small curved work, such as that shown 
in Fig. 5. These tools have to be polished when they become coated 
with metal, the interval between polishings depending on the texture 
of the metal worked and its temper, a shell that has been annealed sev¬ 
eral times coating the tool more than one that has not. It is a quick 
operation to polish the end of a burnisher. A board of soft wood or a 
strip of leather fastened to a board and to the bench, in a position con¬ 
venient to the operator, is used. Grooves are worn into the leather 
or board, and flour of emery and oil, or flint flour and water is used 
to clean the tools, a few passes of a tool being all that is necessary to 
polish it. 







BURNISHING 


31 


Fig. 5 shows samples of burnished work; some of these are spun but 
most of them are drawn in presses. The bright dip which is used to 
clean work before burnishing is composed of: Oil vitriol (sulphuric 
acid), 2 parts; aqua fortis (nitric acid), 1 part. This solution should 
be kept in a crock set in a tank of running water, and mixed 7 or 8 
hours before using, as the acids when combined heat up. It is best to 
mix the acids the day before using. In dipping brass, copper and 
German silver, the parts are strung on a wire whenever possible. If 
there are no holes in the metal that can be used for stringing, they can 
be put in a metal or crock basket, but they cannot be handled to good 
advantage as it is very difficult to thoroughly wash and dip them. 
After stringing the work on a stiff brass or copper wire, it should be 
washed in boiling potash, and then dipped in cold water to clean the 
potash off and cool the metal. 



Fig. 5. Samples of Burnished Work 


After cooling in the water, they are dipped for a few seconds in 
the acids, keeping the work constantly in motion, so that the surfaces 
will be all exposed equally; they are then shaken thoroughly above the 
acid and immediately washed in two separate cold-water baths, then 
in hot soap water, and then in hot water, after which they are dryed 
at once in hot sawdust. This operation will leave a bright, clean sur¬ 
face free from acid. 

Common yellow soap, dissolved to thick paste, is used as a lubricant 
when burnishing brass. The shells and the finger pads are dipped in 
clear water, and the tool is dipped in the soap paste before burnishing 
each shell. 

A lubricant for copper is made by dissolving about one ounce of 
ivory or castile soap in a gallon of water. The shells and pads are 
dipped in this solution, no lubricant being used on the tool. Yellow 
soap should not be used on copper, as the action of the rosin on cop¬ 
per is different from that on brass, the metal being so glazed or 
greased that the tool works badly. 

For copper plate on steel, such as copperized steel oilers, etc., about 
one-half ounce oil vitriol to four gallons of water should be used. The 
burnishing tool should be dipped in a mixture of mutton tallow that 




32 


No. 123—METAL COLORING AND FINISHING 


has been melted with 5 per cent of beeswax, and the work and the 
finger pads should be dipped in the acid mixture. The tool is lubri¬ 
cated in the tallow mixture before burnishing each shell. 

For German silver, the shell should be dipped in clear water, the 
finger pads in sour beer, and the tool in yellow soap paste. 

For white metal or Britannia, use ivory or castile soap in the paste 
form for the tool, and sour beer or ox gall in water (4 ounces to the 
gallon) for the finger pads. Wash the work in hot alkali water (a 
spoonful of cream of tartar, saleratus or soda to a pail of water), and 
dry in hot sawdust. 

For burnishing work which is to be lacquered, without coloring on 
the cloth buff, use thin glue for a lubricant, and also on the finger 
pads. When the part is burnished put it in saleratus water to keep 
it from tarnishing; then wash in hot water and dry in hot sawdust. 
Most plated work can be burnished with the sour beer mixture for 
the finger pads, and castile or ivory soap paste for the tool lubricant. 


CHAPTER V 


THE BALL-BURNISHING PROCESS 

Burnishing, as used in the ordinary sense of the word, consists in 
finishing exterior surfaces of work by rubbing with a highly polished 
steel hand tool, which hardens and polishes the surface metal. The 
Abbott ball-burnishing process produces the same effect, but in an 
entirely different manner, employing quantities of hardened and pol¬ 
ished steel balls which are caused to roll over the work while under 



Fig. 1. Character of Work finished hy Abbott Ball-burnishing Process 

pressure. This pressure is effected by the weight of the balls which 
are confined within a tumbling barrel like that shown in Fig. 2. Thus, 
each ball acts as an individual burnishing tool, and as it rolls over the 
work, pressed by the mass of balls and work above, it leaves a bur¬ 
nished path on the work. Fig. 1 shows some representative burnishing 
jobs which have been efficiently handled by this process. Some idea 
of the action which takes place within the tumbling barrel may be 
gathered by noticing the balls and work which are represented in 
Fig. 3. 

Fig. 4 shows the general form of the ordinary tumbling barrel as 
contrasted with the Abbott burnishing barrel. From this it will be 
seen that in the Abbott barrel, the balls are confined in a deep narrow 
space so that the same amount of balls being restricted within a nar¬ 
rower space exert a heavier burnishing pressure upon the work. The 
Abbott ball-burnishing process cannot be used when any metal is to 






34 


No. 123—METAL COLORING AND FINISHING 


be removed or deep scratches are to be taken out. It is purely and. 
simply a burnishing process for putting a high finish upon the work, 
and on work within its limitations is highly successful. Not only can 
a large amount of work be done in a short space of time, and in a 
very efficient manner, but many jobs which cannot be burnished by 
hand are efficiently finished by this process. Referring to Fig. 3 again, 
it will be seen that it is a simple matter for the balls to burnish the 
inside of a tube, the center of a deep depression, or the inside of a 
wire loop as shown in Fig. 1. Such pieces as these would be difficult 
to burnish in any other 
way. In order to burnish 
corners and depressions, it 
is necessary to employ balls 
small enough to come in 
contact with the surfaces of 
such places; therefore, on 
other than the very plain¬ 
est of work, two sizes of 
balls are commonly used as 
shown in Fig. 3. Again, on 
work which is lettered, 
ordinary polishing processes 
“drag” the letters, but with 
the ball-burnishing process 
this trouble is not experi¬ 
enced. 

The balls used for this 
work are made of low car¬ 
bon steel, by the heading 
process, carbonized and 
hardened clear through and 
then highly polished. The 
balls are not truly spherical, nor of an exact size, but they are highly 
finished and very hard. The barrels may be of the single or multiple 
type, having one or more compartments. The barrel shown in Fig. 7 
has two sections, and gives a general idea of the construction. The 
compartments are octagonal in shape and are lined w r ith maple wood 
so that the balls and work do not come in contact with any metal 
during the burnishing process. Two hand-holes are provided for each 
compartment with covers which may be clamped in place. The two 
hand-holes furnish a means for quickly removing the contents and 
washing out the barrel. A lubricant is employed in burnishing, which 
ordinarily consists of soapy water. 

To burnish a quantity of work, the work and balls are placed in the 
barrel in the proportion of one peck of work to two pecks of steel 
balls. Water is then added until it stands about one inch above the 
contents of the barrel. In this water, about four ounces of burnishing 
soap chips have previously been dissolved. The hand-hole covers are 
then clamped in place, and the mixture tumbled from one to five hours, 



Fig, 2. Type of Burnishing Barrel used 




BURNISHING 


35 


depending upon the character of the work, metal, etc. The speed 
ordinarily employed for tumbling ranges from 10 to 30 R. P. M., the 
usual speed being 15 R. P. M. If after tumbling the work has a dull 
or smutty appearance, the soap solution should be drained from the 
work and clean water substituted, to which should be added a piece of 
cyanide of potassium about the size of a pea. It is highly important 
that the balls be kept from rusting, for rust, of course, destroys their 
burnishing qualities. The balls are easily kept in good condition by 
returning them to the barrel with the soap solution on them, but in 
no event should they be washed in clear water and allowed to stand. 



Fig, 3, View within the Barrel to show Burnishing Action of the Balls 

The burnishing operation is the same on all kinds of metal. After the 
work has been burnished sufficiently, it is separated from the balls by 
dumping the mixture into a screen of sufficiently coarse mesh to allow 
the balls to drop through. A convenient arrangement to use for 
separating the balls from the work is shown in the illustration Fig. 5. 

i 

If the work is not to be plated, it is taken from the barrel and dried 
in sawdust, but if to be plated, it is cleansed in the usual manner and 
plated. The cleaning operation incident to plating is usually very 
troublesome on account of the rouge that is driven into corners of the 
work by the polishing wheels. No such trouble is experienced after 
ball-burnishing, as no rouge is used. It is only necessary to rinse off 
the soap solution, dip in potash and plate. After plating, the work is 
returned to the barrel and tumbled in a soap solution for a half hour 
to impart a high finish. 

While most commonly used for small work, say under three inches 
in greatest dimension, larger work may be handled by a modification 




36 No. 123—METAL COLORING AND FINISHING 

of the process. The difficulty in burnishing large work is due to the 
fact that the weight of the piece is often great enough to injure other 



Hack inery 


Fig. 4. Comparison of Old-style Barrel with Abbott Barrel 



Fig. 5. Convenient Arrangement for Separating Balls and Work 


pieces of work, and, of course, if the pieces are easily bent, there will 
be trouble from this source. Aside from the danger of bending large 
work in the burnishing barrel, a greater source of trouble is from 
scratches caused by the sharp edges of such pieces coming in contact 














































































































































BURNISHING 


37 


with the finished faces of other pieces in the barrel. Referring to the 
illustration Fig. 8 a method of mounting pieces of this character is 
shown. Any convenient method of clamping is employed, depending, 
of course, on the shape of the pieces, but the fundamental idea is to 
support the pieces so that they cannot move in the barrel, and yet give 



the burnishing balls a chance to act upon the work exactly the same 
as though it was loose in the barrel. Mounted in this manner no 
possible injury can be done to the work and yet the balls have access 
to every part of the piece except the edge, even to the inside. It is 
apparent that this method cannot be used for all work, but a little 
ingenuity will often solve the problem without having to resort to 
hand polishing. 











































































38 


No. 123—METAL COLORING AND FINISHING 


A typical installation of the Abott ball burnishing process is found 
at the Heron Mfg. Co., Utica, N. Y. This installation is represented by 
the illustration Fig. 6, in which are shown four double barrels driven 
from a common shaft. A line of piping extends over the four barrels, 
being connected with a hot water tank on the floor above. By means 
of outlets over the barrels, water may be admitted to the barrels for 




mixing the burnishing solutions, and for cleaning the barrels and 
their contents after the burnishing operation. A trolley system is 
arranged so that after the work has been dumped from a barrel into 
a basket, during which operation the suds and soap solution are car¬ 
ried away by means of the trough in front of the barrels, the work 
may be carried to the sawdust box for drying. This sawdust box is 
of the usual type and after the work has been sufficiently dried, it is 



















































































































































BURNISHING 


39 


shoveled into the chute shown at the right of the sawdust box, from 
which it enters the revolving conical screen cylinder and is separated 
from the sawdust, emerging from the small end of the screen, com¬ 
pletely dried and ready for shipment. 

By the use of this apparatus, the Heron Mfg. Co., who manufactures 
casters of all kinds, states that it is producing twice the number of 
parts at half the cost, and getting a better finish than when using hand 
polishers. Thus an expensive polishing and buffing equipment is 
eliminated, as well as the high priced labor formerly employed. 


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margins to allow for binding in sets, should this be desired. These 
books have been enormously successful, but probably would not 
have been, had readers been obliged to pay the usual high prices 
incident to expensive bindings. These books, being made for use 
and not for ornament, are bound in strong paper covers, which 
enables marketing them at an unprecedented price for books of 
the highest merit. 

The plan comprehends an indefinite number of compact, inex¬ 
pensive books, each covering one subject thoroughly in a practical 
manner, and sold singly, or in complete sets, as may be desired. 
The whole series comprises a complete working library of au¬ 
thentic mechanical literature for the Mechanical Engineer, the 
Machine Designer and Draftsman, the Machinist, the Toolmaker 
and the Apprentice. The books are particularly adapted for self- 
education and are planned to meet the demand for a reliable, 
practical and inexpensive system. 

The information contained in the books of this System is the 
latest and best available on machine design, construction and 
operation, revised and brought up to date by Machinery’s edi¬ 
torial staff—men constantly in touch with the best sources of 
information, and with the latest developments in mechanical 
practice. 

These books are for the practical men at work in the me¬ 
chanical industries. They deal in a practical manner with actual 
mechanical problems. They describe the practice and explain 
the mechanical principles in clear and simple language and in a 
direct and straightforward, manner. The whole idea of the books 
is to give the greatest possible amount of definite, practical in¬ 
formation, in the clearest manner and in the smallest amount of 
space practicable. The information is boiled down. 

Machinery 

The Industrial Press Machinery Publishing Co., ltd. 

140-148 Lafayette Street 27, Chancery Lane 

New York, U.S.a. London, W. C. 








/ 


- 1 . 

Nu. 72. 


Gers. 

-oiler Furnaces and Chimneys. 
Feed Water Appliances. 

Steam Engines. 

Steam Turbines. 

Pumps, Condensers, Steam and 
Piping. 


HEATING AND VENTILATION 


Water 


LOCOMOTIVE DESIGN AND RAILWAY SHOP 
PRACTICE 


No. 

27. 

No. 

28. 

No. 

29. 

No. 

30. 

No. 

79. 

No. 

80. 

* No. 

81. 

No. 

82. 

No. 

83. 

No. 

84. 

No. 

90. 


Locomotive Design, Part I. 
Locomotive Design, Part II. 
Locomotive Design, Part III. 


and Side 
Wheels; Axles; 

1 

and 


Locomotive Building. — Main 
Rods. 

Locomotive Building. 

Driving Boxes. 

Locomotive Building. — Cylinders 
Frames. 

Locomotive Building.—Valve Motion. 

Locomotive Building.—Boiler Shop Prac¬ 
tice. 

Locomotive Building.—Erecting. 

Railway Repair Shop Practice. 


ELECTRICITY—DYNAMOS AND MOTORS 


No. 34. 
No. 73. 


No. 74. 


No.. 75. 
No. 76. 
No. 77. 
No. 78. 
No 115. 


Care and Repair of Dynamos and Motors. 
Principles and Applications of Electricity. 
—Static Electricity; Electrical Measure¬ 
ments; Batteries. 

Principles and Applications of Electricity. 
—Magnetism; Electric-Magnetism; Elec¬ 
tro-Plating. 

Principles and Applications of Electricity. 
—Dynamos; Motors; Electric Railways. 
Principles and Applications of Electricity. 
—Telegraph and Telephone. 

Principles and Applications of Electricity. 
—Electric Lighting. 

Principles and Applications of Electricity. 
—Transmission of Power. 

Electric Motor Drive for Machine Tools. 


No. 39. Fans, Ventilation and Heating. 

No. 66. Heating and Ventilation of Shops and 
Offices. 


IRON AND STEEL 


No. 36. Iron and Steel. 

No. 62. Hardness and Durability Testing 
Metals. 

No. 117. High-speed and Carbon Tool Steel. 
No. 118. Alloy Steels. 


of 


FORGING 


No. 44. Machine Blacksmithing. 

No. 45. Drop Forging. 

No. 61. Blacksmith Shop Practice. 

No. 113. Bolt, Nut and Rivet Forging. 
No. 114. Machine Forging. 

No. 119. Cold Heading. 


MECHANICAL DRAWING AND DRAFTING- 
ROOM PRACTICE 


No. 2. Drafting-Room Practice. 


No. 8. Working Drawings and Drafting-Room 
Kinks. 


No. 33. Systems and Practice of the Drafting- 
Room. 

No. 85. Mechanical Drawing.—Geometrical Prob¬ 
lems. 


No. 86. Mechanical Drawing.-—Projection. 

No. 87. Mechanical Drawing.—Machine Details. 
No. 88. Mechanical Drawing.—Machine Details. 


DIE-CASTING 


No. 108. Die-Casting Machines. 

No. 109. Die-Casting, Dies and Methods. 


MISCELLANEOUS 


No. 35. Tables and Formulas for Shop and Draft¬ 
ing-Room. 

No. 110. Extrusion of Metals. 


MACHINERY’S DATA BOOKS 

Machinery’s Data Books include the material in the well-known series of Data 
Sheets published by Machinery during the past fifteen years. Of these Data Sheets, 
nearly 700 were published and 7,000,000 copies sold. Revised and greatly amplified, 
they are now presented in book form, kindred subjects grouped together. The price 
of each book is 25 cents (one shilling) delivered anywhere in the world. 


.... - 









No. 

1. 

No. 

2. 

No. 

3. 

No. 

4. 

No. 

5. 

No. 

6. 

No. 

7. 

No. 

8 

No. 

9. 

No. 

10. 


LIST OF MACHINERY’S DATA BOOKS 


Screw Threads. 

Screws, Bolts and Nuts. 

Taps and Dies. 

Reamers, Sockets, Drills and Milling Cut¬ 
ters. 

Spur Gearing. 

Bevel, Spiral and Worm Gearing. 
Shafting, Keys and Keyways. 

Bearings, Couplings, Clutches, Crane 
Chain and Hooks. 

Springs, Slides and Machine Details. 
Motor Drive, Speeds and Feeds, Change 
Gearing, and Boring Bars. 


No. 11. 

No. 12. 
No. 13. 
No. 14. 
No. 15. 
No. 16. 
No. 17. 
No. 18. 
No. 19. 
No. 20. 


Milling Machine Indexing, Clamping De¬ 
vices and Planer Jacks. 

Pipe and Pipe Fittings. 

Boilers and Chimneys. 

Locomotive and Railway Data. 

Steam and Gas Engines. 

Mathematical Tables. 

Mechanics and Strength of Materials. 
Beam Formulas and Structural Design. 
Belt, Rope and Chain Drives. 

Wiring Diagrams, Heating and Ventila¬ 
tion and Miscellaneous Tables. 






LIBRARY OF CONGRESS 


0 017 108 154 3 ^ \ 

MACHINERY’S, 

HANDBOOK 

For MACHINE SHOP 
AND DRAFTING-ROOM 



A REFERENCE BOOK ON MACHINE 
DESIGN AND SHOP PRACTICE FOR 
THE MECHANICAL ENGINEER, 
DRAFTSMAN, TOOLMAKER AND 
MACHINIST. 


Machinery’s Handbook comprises nearly 1400 pages of carefully edited and 
condensed data relating to the theory and practice of the machine-building 
industries. It is the first and only complete handbook devoted exclusively to 
the metal-working field, and contains' in compact and condensed form the 
information and data collected by Machinery during the past twenty years. 
It is the one essential book in a library of mechanical literature, because it 
contains all that is of importance in the text-books and treatises on mechanical 
engineering practice. Price $5.00. 

GENERAL CONTENTS 

Mathematical tables—Principal methods and formulas in arithmetic and algebra— 
Logarithms and logarithmic tables—Areas and volumes—Solution of triangles and 
trigonometrical tables—Geometrical propositions and problems—Mechanics—Strength of 
materials—Riveting and riveted joints—Strength and properties of steel wire—Strength 
and properties of wire rope—Formulas and tables for spring design—Torsional strength 
—Shafting—Friction—P’ain, roller and ball bearings—Keys and keyways—Clutches and 
couplings—Friction brakes—Cams, cam design and cam milling—Spur gearing—Bevel 
gearing—Spiral gearing—Herringbone gearing—Worm gearing—Epicyclic gearing—Belting 
and rope drives—Transmission chain and chain drives—Crane chain—Dimensions of small 
machine details—Speeds and feeds of machine tools—Shrinkage and force fit allowances— 
Measuring tools and gaging methods—Change gears for spiral milling—Milling machine 
indexing—Jigs and fixtures—Grinding and grinding wheels—Screw thread systems and 
thread gages—Taps and threading dies—Milling cutters—Reamers, counterbores and 
twist drills—Heat-treatment of steel—Hardening, casehardening, annealing—Testing the 
hardness of metals—Foundry and pattern shop information—The welding of metals— 
Autogenous welding—Thermit welding—Machine welding—Blacksmith shop information 
—Die casting—Extrusion process—Soldering and brazing—Etching and etching fluids— 
Coloring metals—Machinery foundations—Application of motors to machine tools—Dynamo 
and motor troubles—Weights and measures—Metric system—Conversion tables—Specific 
gravity—Weights of materials—Heat—Pneumatics—Water pressure and flow of water— 

Pipes and piping—Lutes and cements—Patents. 


Machinery, the leading journal in the machine-building field, the originator 
of the 25-cent Reference and Data Books. Published monthly. Subscription, 
$2.00 yearly. Foreign subscription, $3.00. 

THE INDUSTRIAL PRESS, Publishers of MACHINERY 
140-148 LAFAYETTE STREET 


NEW YORK CITY, U. S. A. 













































































